rabies

Rabies

Definition

Rabies is an acute viral disease of the central nervous system that affects humans and other mammals but is most common in carnivores (flesh-eaters). It is sometimes referred to as a zoonosis, or disease of animals that can be communicated to humans. Rabies is almost exclusively transmitted through saliva from the bite of an infected animal. Another name for the disease is hydrophobia, which literally means "fear of water," a symptom shared by half of all people infected with rabies. Other symptoms include fever, depression, confusion, painful muscle spasms, sensitivity to touch, loud noise, and light, extreme thirst, painful swallowing, excessive salivation, and loss of muscle tone. If rabies is not prevented by immunization, it is almost always fatal.

Description

Cases of rabies in humans are very infrequent in the United States and Canada, averaging one or two a year (down from over 100 cases annually in 1900), but the worldwide incidence is estimated to be between 30,000 and 50,000 cases each year. These figures are based on data collected by the World Health Organization (WHO) in 1997 and updated in 2002. Rabies is most common in developing countries in Africa, Latin America, and Asia, particularly India. Dog bites are the major origin of infection for humans in developing countries, but other important host animals may include the wolf, mongoose, raccoon, jackal, and bat. A group of researchers in India found that monkeys as well as dogs were frequent vectors of rabies. The team also reported that the male:female ratio of rabies patients in India is 4:1.

Most deaths from rabies in the United States and Canada result from bat bites; the most recent fatality was a 66-year-old man in California who died in September 2003. The death of a nine-year-old girl in Quebec in the fall of 2000 was the first case of human rabies in Canada since 1985. Public health officials eventually determined that the girl had been bitten while she was sleeping by a silver-haired bat that had gotten into the family's home.

On October 18, 2004, a Wisconsin teenager was diagnosed with full-blown rabies after suffering from a minor bat bite on September 12, 2004. Miraculously, she was cured of rabies after doctors induced coma and administered four antiviral drugs to her. Since the therapy was only given and successful for one case, its curative properties needs to be corroborated by other cases before it will be considered a viable treatment option. The case and the physicians' findings will be published in a medical journal.

People whose work frequently brings them in contact with animals are considered to be at higher risk than the general population. This would include those in the fields of veterinary medicine, animal control, wildlife work, and laboratory work involving live rabies virus. People in these occupations and residents of or travelers to areas where rabies is a widespread problem should consider being immunized.

In late 2002, rabies re-emerged as an important public health issue. Dr. Charles E. Rupprecht, director of the World Health Organization (WHO) Collaborating Center for Rabies Reference and Research, has listed several factors responsible for the increase in the number of rabies cases worldwide:

Rapid evolution of the rabies virus. Bats in the United States have developed a particularly infectious form of the virus.

Increased diversity of animal hosts for the disease.

Changes in the environment that are bringing people and domestic pets into closer contact with infected wildlife.

Increased movement of people and animals across international borders. In one recent case, a man who had contracted rabies in the Philippines was not diagnosed until he began to feel ill in the United Kingdom.

Lack of advocacy about rabies.

Causes and symptoms

Rabies is caused by a rod- or bullet-shaped virus that belongs to the family Rhabdoviridae. The rabies virus is a member of a genus of viruses called lyssaviruses, which include several related viruses that infect insects as well as mammals. The rabies virus is usually transmitted via an animal bite, however, cases have also been reported in which the virus penetrated the body through infected saliva, moist tissues such as the eyes or lips, a scratch on the skin, or the transplantation of infected tissues. Inhalation of the virus in the air, as might occur in a highly populated bat cave, is also thought to occur.

From the bite or other area of penetration, the virus multiplies as it spreads along nerves that travel away from the spinal cord and brain (efferent nerves) and into the salivary glands. The rabies virus may lie dormant in the body for several weeks or months, but rarely much longer, before symptoms appear. Initially, the area around the bite may burn and be painful. Early symptoms may also include a sore throat, low-grade fever, headache, loss of appetite, nausea and vomiting, and diarrhea. Painful spasms develop in the muscles that control breathing and swallowing. The individual may begin to drool thick saliva and may have dilated or irregular pupils, increased tears and perspiration, and low blood pressure.

Later, as the disease progresses, the patient becomes agitated and combative and may exhibit increased mental confusion. The affected person usually becomes sensitive to touch, loud noises, and bright lights. The victim also becomes extremely thirsty, but is unable to drink because swallowing is painful. Some patients begin to dread water because of the painful spasms that occur. Other severe symptoms during the later stage of the disease include excessive salivation, dehydration, and loss of muscle tone. Death usually occurs three to 20 days after symptoms have developed. Unfortunately, recovery is very rare.

Diagnosis

After the onset of symptoms, blood tests and cerebrospinal fluid (CSF) analysis tests will be conducted. CSF will be collected during a procedure called a lumbar puncture in which a needle is used to withdraw a sample of CSF from the area around the spinal cord. The CSF tests do not confirm diagnosis but are useful in ruling out other potential causes for the patient's altered mental state.

The two most common diagnostic tests are the fluorescent antibody test and isolation of the rabies virus from an individual's saliva or throat culture. The fluorescent antibody test involves taking a small sample of skin (biopsy) from the back of the neck of the patient. If specific proteins, called antibodies, that are produced only in response to the rabies virus are present, they will bind with the fluorescent dye and become visible. Another diagnostic procedure involves taking a corneal impression in which a swab or slide is pressed lightly against the cornea of the eye to determine whether viral material is present.

Treatment

Until the most recent successful cure of a late-term rabies case can be validated with further success and validation from the medical community, the historic treatment options for rabies prevention immediately following a bite remains the most viable treatment. Because of the extremely serious nature of a rabies infection, the need for rabies immunizations will be carefully considered for anyone who has been bitten by an animal, based on a personal history and results of diagnostic tests.

If necessary, treatment includes the following:

The wound is washed thoroughly with medicinal soap and water. Deep puncture wounds should be flushed with a catheter and soapy water. Unless absolutely necessary, a wound should not be sutured.

Rabies vaccination may or not be given, based on the available information. If the individual was bitten by a domestic animal and the animal was captured, the animal will be placed under observation in quarantine for ten days. If the animal does not develop rabies within four to seven days, then no immunizations are required. If the animal is suspected of being rabid, it is killed, and the brain is examined for evidence of rabies infection. In cases involving bites from domestic animals where the animal is not available for examination, the decision for vaccination is made based on the prevalence of rabies within the region where the bite occurred. If the bite was from a wild animal and the animal was captured, it is generally killed because the incubation period of rabies is unknown in most wild animals.

If necessary, the patient is vaccinated immediately, generally through the administration of human rabies immune globulin (HRIG) for passive immunization, followed by human diploid cell vaccine (HDCV) or rabies vaccine adsorbed (RVA) for active immunization. Passive immunization is designed to provide the individual with antibodies from an already immunized individual, while active immunization involves stimulating the individual's own immune system to produce antibodies against the rabies virus. Both rabies vaccines are equally effective and carry a lower risk of side effects than some earlier treatments. Unfortunately, however, in underdeveloped countries, these newer vaccines are usually not available. Antibodies are administered to the patient in a process called passive immunization. To do this, the HRIG vaccine is administered once, at the beginning of treatment. Half of the dose is given around the bite area, and the rest is given in the muscle. Inactivated viral material (antigenic) is then given to stimulate the patient's own immune system to produce antibodies against rabies. For active immunization, either the HDCV or RVA vaccine is given in a series of five injections. Immunizations are typically given on days one, three, seven, 14, and 28.

In those rare instances in which rabies has progressed beyond the point where immunization would be effective, the groundbreaking treatment involving a drug-induced coma and the administration of four different antiviral drugs will most likely be a radical treatment option. The traditional approach prior to October 2004 was to provide as much relief from pain and suffering as possible through medical intervention while waiting to see if survival was possible. The patient would be given medication to prevent seizures, relieve some of the anxiety, and relieve painful muscle spasms. Pain relievers would also be given. In the later stages, aggressive supportive care would be provided to maintain breathing and heart function. Survival via the traditional treatment is rare but can occur.

Prognosis

If preventative treatment is sought promptly, rabies need not be fatal. Immunization is almost always effective if started within two days of the bite. Chance of effectiveness declines, however, the longer vaccination is put off. It is, however, important to start immunizations, even if it has been weeks or months following a suspected rabid animal bite, because the vaccine can be effective even in these cases. If immunizations do not prove effective or are not received, rabies is nearly always fatal with a few days of the onset of symptoms.

Key terms

Active immunization — Treatment that provides immunity by challenging an individual's own immune system to produce antibody against a particular organism, in this case the rabies virus.

Antibody — A specific protein produced by the immune system in response to a specific foreign protein or particle called an antigen.

Biopsy — The removal of a small sample of tissue for diagnostic purposes.

Efferent nerves — Nerves that convey impulses away from the central nervous system to the periphery.

Lumbar puncture — A procedure that involves withdrawing a small sample of cerebrospinal fluid from the back around the spinal cord.

Lyssavirus — A genus of viruses that includes the rabies virus and related viruses that infect insects as well as mammals.

Passive immunization — Treatment that provides immunity through the transfer of antibodies obtained from an immune individual.

Rhabdovirus — A type of virus named for its rod- or bullet-like shape. The rabies virus belongs to a family of viruses called Rhabdoviridae.

Vector — An animal or insect that carries a disease-producing organism.

Zoonosis — Any disease of animals that can be transmitted to humans. Rabies is an example of a zoonosis.

As of October 2004, the medical community awaits the publication of findings by the doctors that administered a life-saving treatment that cured a Wisconsin teenager of full-blown rabies. Further test cases will prove whether or not this treatment option will be a historic development in the search for a cure for rabies.

Prevention

One promising preventive strategy that has been used since the early 2000s is the distribution of wildlife baits containing an oral vaccine against rabies. This strategy has been used in Germany to vaccinate wild foxes, which are frequent carriers of the disease in Europe. In the United States, veterinary researchers at Kansas State University have developed an oral vaccine for fruit bats; early trials of the vaccine have given promising results.

The following precautions should be observed in environments where humans and animals may likely come into contact.

Domesticated animals, including household pets, should be vaccinated against rabies. If a pet is bitten by an animal suspected to have rabies, its owner should contact a veterinarian immediately and notify the local animal control authorities. Domestic pets with current vaccinations should be revaccinated immediately; unvaccinated dogs, cats, or ferrets are usually euthanized (put to sleep). Further information about domestic pets and rabies is available on the American Veterinary Medical Association (AVMA) web site.

Wild animals should not be touched or petted, no matter how friendly they may appear. It is also important not to touch an animal that appears ill or passive, or whose behavior seems odd, such as failing to show the normal fear of humans. These are all possible signs of rabies. Many animals, such as raccoons and skunks, are nocturnal and their activity during the day should be regarded as suspicious.

People should not interfere in fights between animals.

Because rabies is transmitted through saliva, a person should wear rubber gloves when handling a pet that has had an encounter with a wild animal.

Garbage or pet food should not be left outside the house or camp site because it may attract wild or stray animals.

Windows and doors should be screened. Some victims of rabies have been attacked by infected animals, particularly bats, that entered through unprotected openings.

State or county health departments should be consulted for information about the prevalence of rabies in an area. Some areas, such as New York City, have been rabies-free, only to have the disease reintroduced at a later time.

Preventative vaccination against rabies should be considered if one's occupation involves frequent contact with wild animals or non-immunized domestic animals.

Bites from mice, rats, or squirrels rarely require rabies prevention because these rodents are typically killed by any encounter with a larger, rabid animal, and would, therefore, not be carriers.

Travelers should ask about the prevalence of the disease in countries they plan to visit.

Periodicals

Deshaies, D., P. A. Pilon, L. Valiquette, and J. Carsley. "A Public Health Intervention at the Time of a Case of Rabies in Quebec." [in French] Canadian Journal of Public Health 95 (March-April 2004): 138-141.

rabies

[ra´bēz, ra´be-ēz]

an acute infectious disease of the central nervous system, which affects all warm-blooded animals, including humans. It is caused by an RNA virus of the genus Lyssavirus. The virus is often present in the host's saliva, and human infection is usually transmitted by the bite or lick of a rabid animal, such as a bat, wolf, dog, cat, or other mammal; it is sometimes transmitted by the respiratory route. The incubation period in humans is from one to three months, being shorter following bites near the brain.

The earliest symptoms are intermittent pain, numbness, tingling, or burning around the site of infection; soon afterward, generalized hyperexcitability occurs, followed by fever, paralysis of the muscles of swallowing, and glottal spasm brought on by the sight of fluids or the drinking of fluids, and by maniacal behavior. Convulsions, tetany, and respiratory paralysis are the inevitable terminal events in untreated cases. The diagnosis can be determined by viral isolation (from saliva, cerebrospinal fluid, urine) or by demonstration of neutralizing antibody, and after death by the appearance of cytoplasmic inclusion bodies (Negri bodies) in degenerated neurons.

Without adequate immunization and treatment a person who has been infected with rabies is not likely to survive.

Prevention. All warm-blooded family pets (such as dogs, cats, and monkeys) should be vaccinated against rabies periodically.

It is also essential to learn to recognize a rabid animal. In the early “anxiety” stages, a rabid animal may have a change of temperament. Many, including wild animals, may become unusually friendly. The rabid animal may next enter a “furious” stage, in which it wanders about biting everything that moves, and even some things that do not move, such as sticks and stones. It then develops paralysis of the throat, which makes swallowing difficult. The name hydrophobia, “fear of water,” was given to the disease because it was observed that stricken animals avoided water. Actually, this is not because of fear of water, but because they cannot swallow. Saliva often drips from the animal's mouth and may be whipped into a foam.

Some animals pass directly from the anxiety stage to paralysis without becoming violent. This is called the “dumb” form of rabies. The animal may appear to have something caught in its throat. A dog with something in its throat usually tries to remove it, but a rabid dog will not do this. Eventually all of the rabid animal's muscles become paralyzed and it dies.

Treatment. When a person is bitten by an animal, the wound should be washed thoroughly with soap and water, and then treated like any other wound. It is extremely important to seek emergency health care immediately. If possible, steps should be taken to find out if the biting animal has rabies, preferably by finding the animal and confining it for observation. When the biting animal must be killed in order to capture it, care must be taken to see that the head is not damaged, so that the brain can be examined to establish a diagnosis. If the biting animal cannot be caught for observation, the bitten person must be given antirabies treatment immediately.

Preventive treatment of suspected rabies is based on immunization by a series of vaccine and immune serum injections. When bites are in areas close to the head or in areas with many nerve endings, such as the hands, the virus may reach the brain quickly. In such cases treatment should start immediately, even though the suspected animal is still being observed.

Agents used to confer passive immunity are human rabies immune globulin and anitrabies serum. Allergic reactions to the immune globulin are rare, making it the preferred agent. In response to administration of antirabies serum, an occasional patient may experience severe anaphylaxis, while others develop serum sickness; hence, this agent is given only when human rabies immune globulin is not available. In many patients, the serum antibodies produce permanent immunity only after the last booster. If active immunity has been established, however, it lasts a lifetime. If a patient does not have permanent immunity established by the vaccine, the Centers for Disease Control and Prevention should be contacted.

A more effective and less troublesome immunizing agent is the newer human diploid cell vaccine. It requires only five injections over 28 days.

There is no cure for rabies and once symptoms appear treatment can only be palliative. This includes sedation of the patient and provision of a quiet environment to reduce anxiety and relieve pain, administration of a powerful muscle relaxant (curare-like drugs) to reduce muscular contractions, and supportive measures to maintain urinary and respiratory function. Death occurs in 2 to 5 days.

ra·bies

(rā'bēz), Although the Latin word is correctly pronounced in three syllables, speakers of English virtually always reduce these to two.

Highly fatal infectious disease that may affect all species of warm-blooded animals, including humans; transmitted by the bite of infected animals including dogs, cats, skunks, wolves, foxes, raccoons, and bats, and caused by a neurotropic species of Lyssavirus, a member of the family Rhabdoviridae, that has tropism for the central nervous system and the salivary glands; inhalation infection possbile (aerosolized virus in bat caves, attics). The symptoms are characteristic of a profound disturbance of the nervous system, for example, excitement, aggressiveness, and madness, followed by paralysis and death. In animals, clinical signs are variable, and sometimes drooling and tongue paralysis are the only signs. Transmission of the virus can occur before clinical signs are expressed. Characteristic cytoplasmic inclusion bodies (Negri bodies) found in many neurons aid rapid laboratory diagnosis.

rabies

/ra·bies/ (ra´bēz) (ra´be-ēz) an acute, usually fatal, infectious viral disease of the central nervous system of mammals, human infection resulting from the bite of a rabid animal (bats, dogs, etc.). In the later stages, it is marked by paralysis of the muscles of deglutition and glottal spasm provoked by the drinking or the sight of liquids, and by maniacal behavior, convulsions, tetany, and respiratory paralysis.rab´id

rabies

(rā′bēz)

n.

An acute, infectious, usually fatal viral disease of the central nervous system that is transmitted by the bite of infected animals and occurs in many mammals, including dogs, cats, raccoons, and bats.

ra′bi·et′ic(-ĕt′ĭk) adj.

rabies

[rā′bēz]

Etymology: L, rabere, to rave

an acute, usually fatal viral disease of the central nervous system of mammals. It is transmitted from animals to people through infected saliva. rabid /rab′id/,adj.

observations The reservoir of the virus is chiefly wild animals, including skunks, bats, foxes, and raccoons, and unvaccinated dogs and cats. After introduction into the human body, often by a bite of an infected animal, the virus travels along nerve pathways to the brain and later to other organs. An incubation period ranges from 10 days to 1 year and is followed by a prodromal period characterized by fever, malaise, headache, paresthesia, and myalgia. After several days severe encephalitis, delirium, agonizingly painful muscular spasms, seizures, paralysis, coma, and death ensue.

interventions Few nonfatal cases have been documented in humans; survival in those cases has been the result of intensive supportive nursing and medical care. There is no treatment once the virus has reached the tissue of the nervous system. Local treatment of wounds inflicted by rabid animals may prevent the disease. The wound is cleansed with soap, water, and a disinfectant. A deep wound may be cauterized and rabies immune globulin injected directly into the base of the wound. For active immunization a series of three intramuscular injections with adsorbed vaccine (RVA), purified chick embryo cell vaccine, or human diploid cell rabies vaccine is begun. If vaccine is administered, intramuscular injection is given on days 0, 7, and 21 or 28. Great effort is made to locate and examine the animal. The animal that is suspected of being rabid is not immediately killed but put in isolation and carefully observed. If the animal is well in 10 days, there is little danger of rabies developing from the bite. Tissue from the animal's brain may be examined microscopically or by fluorescent antibody screening techniques.

nursing considerations Rabies virus infection can be eradicated from most communities by prophylactic immunization of domestic animals, stringent measures for the control of domestic animals, and elimination of any wild animals acting as reservoirs of infection. A preexposure vaccination is advised for those at risk, such as veterinarians, animal handlers, and some laboratory workers. The nurse and other health workers may encourage compliance with such efforts and teach the necessity of avoiding direct contact with wild animals and the importance of immediate first aid for any animal bite and reporting such contact to health care providers.

rabies

A fatal infection rabiesvirus which follows 'injection' by an animal bite; the virion crosses the neuromuscular junction and infects nerves, spreading centripetally into the CNS and centrifugally into the salivary glands of mammals Epidemiology Human rabies is rare 1 to 2 cases/year in US; internationally, 33,000 people die/yr from rabies in Asia, Africa Clinical 18-60 day incubation, followed by nonspecific Sx–eg, fever, headache, N&V, numbness at site of exposure, and early neurologic signs–anxiety, restlessness, depression; acute neurologic phase is characterized by agitation, confusion, delirium hydrophobia, laryngeal spasms, paralysis, complications Vaccination VRG vaccine. See Negri bodies. Cf Pseudo-rabies.

ra·bies

(rā'bēz)

Highly fatal infectious disease transmitted by the bite of infected animals, including dogs, cats, skunks, wolves, foxes, raccoons, and bats, and caused by a neurotropic lyssavirus that replicates in the central nervous system and the salivary glands. The symptoms are excitement, aggressiveness, and madness, followed by paralysis and death. Characteristic cytoplasmic inclusion bodies (Negri bodies) found in many of the neurons are an aid to rapid laboratory diagnosis. Synonym(s): hydrophobia.

Rabies

A nervous system disease that affects many different animals. Rabies is a brain inflammation (encephalitis) caused by a lyssavirus, a member of the rhabdovirus family, that enters the nervous system at the site of a bite by a rabid animal. The time taken for the virus to reach the brain and cause the disease varies with the distance of the bite from the brain, and may be from 10 days to 3 or 4 months. Rabies starts with fever, headache, neck stiffness, anxiety and disorientation. Soon there is acute fear of swallowing because of violent spasms of the throat and diaphragm causing gagging, choking and extreme panic. Seizures, delusions and hallucinations then occur, followed by coma and death, usually within a week of the start of the severe symptoms. Careful cleaning of bites and the use of human antirabies globulin and rabies vaccine can prevent the disease. There is no specific treatment for the established encephalitis. Also known as hydrophobia on account of a principal symptom.

rabies

an ACUTE viral disease of the nervous system in many mammals, particularly man, dogs, cattle and foxes, resulting in degeneration of the spinal cord and brain, leading to death. Entry of the virus is usually by a wound or skin abrasion caused by a rabid animal. The incubation period is usually 3–8 weeks, the first signs being increased muscle tone and extreme difficulty in swallowing. The spasmodic contractions of the throat muscles that cause swallowing may become extremely painful and contraction may even be triggered by the sight of water. Thus individuals are described as hydrophobic. Despite recent advances, infected individuals must be vaccinated in the first few days after infection for effective treatment.

ra·bies

(rā'bēz)

Highly fatal infectious disease that may affect all species of warm-blooded animals, including humans; transmitted by the bite of infected animals and caused by a neurotropic species of Lyssavirus. Synonym(s): hydrophobia.

rabies (rā´bēz),

n an acute, usually fatal viral disease of the central nervous system of animals. It is transmitted from animals to humans by infected blood, tissue, or most commonly, saliva.

rabies

a highly fatal viral infection of the nervous system which affects all warm-blooded animal species. The causative rhabdovirus is transmitted in the saliva and the principal method of infection in animals is by a bite. Separate furious and dumb (paralytic) forms are described but both commonly occur in the one animal. The syndrome includes an ascending paralysis which may be preceded by a period of mania and aggression. Rabies is one of the most important of the zoonoses because of the inevitably fatal outcome for the infected human.

bat rabies

an infection which is endemic in bats and may be caused by the rabies virus or by other similar rhabdoviruses such as Lagos, Mokola and Australian flying fox bat viruses.

present in the salivary glands and brain tissue of infected animals and may make the tissue nonlethal for mice by the intracerebral route. It does not interfere with detection of rabies antigen by immunofluorescent staining.

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